Answer
When a wave spring is compressed from its free height ($H_f$) toward its work height ($H_w$) or solid height ($H_s$), the waves flatten, causing the mean diameter $D_m$ to increase due to the geometry of the arc segments. The approximate expansion $Δ D$ can be estimated using the relationship $Δ D = 0.02 \cdot \frac{(H_f - H_w)^2}{D_m}$. In tight-tolerance bore installations, this radial growth is critical to prevent binding. Engineers must calculate the 'Maximum Expanded OD' using $OD_{max} = OD_{free} + \sqrt{L^2 + R^2} - R$, where $L$ is the wave length and $R$ is the radius of curvature. If the spring is constrained by a bore, this expansion induces secondary hoop stresses that can lead to premature yielding or 'scuffing' against the bore wall, necessitating a reduction in the initial OD specification.
